Check your theme, and ensure you actually do have the fonts. The log suggests it's trying to load an XMB font (default if no type specified). This is caused by the server configuration so closing this issue.
Please change your theme to use a specific xft font and try again. For example, instead of "fixed#Left" use "Sans-8:Bold#XFT". I suppose that will fix it.
Which theme and what OS are you experiencing this on? What does the locale command output?